From the viewpoints of resources and energy saving and environmental protection, social needs for reduction in carbon dioxide gas emission have been increasing in recent years. For automobiles, various measures such as weight saving and use of electric energy have also been considered. Thus, tires for automobiles are needed to improve in properties such as abrasion resistance and durability to contribute to resources saving. Therefore, various improvements to rubber compositions for tires have been considered.
For example, a known technique to improve properties including abrasion resistance is to reduce the sulfur content in a rubber composition for a tire, but this leads to the problem of deterioration of fuel economy. Another proposed technique is to prepare a masterbatch to enhance the dispersibility of silica. However, this poses problems in that, for example, a masterbatch containing butadiene rubber and silica is poor in texture so that the masterbatch is difficult to feed in the form of a sheet, and therefore has lower processability. As described above, since the properties including abrasion resistance, fuel economy, and processability are generally difficult to improve in a balanced manner, improvements thereof are needed.